The embryonic Stem Cell Technology Core will assist in the design and construction of genetically modified mice. Two technicians under the direction of Dr. Bradley will be responsible for several essential protocols, including growth and transformation of murine ES cells; selection of an DNA isolation from potential recombinant cells; introduction of mutant cells into mouse blastocysts; and testing transmission of the desired modification. It is estimated that the Core will handle 12-15 new ES, and thus mouse, lines per year.